Posted
by
BeauHDon Saturday August 12, 2017 @02:00AM
from the back-from-the-dead dept.

Big Hairy Ian shares a report from New Atlas: When the first manned mission to Mars sets out, it may be on the tail of an atomic rocket engine. The Space Race vintage technology could have a renaissance at NASA after the space agency's Marshall Space Flight Center in Huntsville, Alabama signed a contract with BWXT Nuclear Energy to develop updated Nuclear Thermal Propulsion (NTP) concepts and new fuel elements to power them.

Today, with NASA once again considering the challenges of sending astronauts to Mars, the nuclear option is back on the table as part of the agency's Game Changing Development program. Under this, NASA has awarded BMXT, which supplies nuclear fuel to the U.S. Navy, a $18.8-million contract running through September 30, 2019 to look into the possibility of developing a new engine using a new type of fuel. Unlike previous designs using highly enriched uranium, BMXT will study the use of Low-Enriched Uranium (LEU), which has less than 20 percent of fissile uranium 235. This will provide a number of advantages. Not only is it safer than the highly enriched fuel, but the security arrangements are less burdensome, and the handling regulations are the same as those of a university research reactor. If NASA determines next month that the LEU engine is feasible, the project will conduct testing and refine the manufacturing process of the Cermet fuel elements over the course of a year, with testing of the full-length Cermet fuel rods to be conducted at Marshall.

Slashdot reader Big Hairy Ian adds: "At the very least it looks much more feasible than Project Orion."

Look at what a horrific disaster all those exploding reactors have been on navy ships and submarines!

It's the man, not the machine. Rickover is the man. The way Thresher imploded sounded like a pretty gruesome way to go, at least it was quick. I think it was that disaster that drove safety into the certification of the subs for a certain depth.

Not to mention the ecological disaster that there would be if evil radiation were to leak in space!

It would be a great use in space. Not so keen on them launching with them. Great that it's LEU, that engine would still be pretty hot coming back, so yeah as long as it stays in space it would be great.

Look at what a horrific disaster all those exploding reactors have been on navy ships and submarines!When will people realize the horror of nuclear reactors! Radiation! Radiation!

Remove the sensationalist word "exploding", and yes. Sunken nuclear subs [wikipedia.org] are a problem. Kursk, K-159 and Komsomolets are of concern to the Norwegians, and radioactive leaks are either already registered or are predicted to occur within a few years.

Monitoring of those wrecks and of the three dumped reactors from the Lenin (nuclear icebreaker) have shown that radioactivity is barely detectable 50cm from the reactors and totally undetectable from 2 metres away

The Lenin reactors in particular have been subjected to intense scrutiny over the years because they lie very close to Norwegian territorial waters and they were/are rightfully worried about them.

Not to mention the ecological disaster that there would be if evil radiation were to leak in space!Do people not realize it is the one truly pristine environment left?

I can see that you are no scientist because your facts are wrong. Radiation is a natural phenomenon in the environment on Earth and in Space. We need to avoid being exposed to too much radiation because that can kill.

Space can have high levels of radiation depending on how close you get to the source. The main source of radiation in the solar system is the Sun and you would die without the radiation from the Sun. The Earth's magnetic field and atmosphere help to prevent damaging radiation from hitting the E

Come on. You can die even if you strap yourself behind a horse. You remind me of people who said (about 2 centuries ago) that going over 40 km/hours kills a human.Speed doesn't killAcceleration may kill (solution, don't accelerate beyond harmful limits).Radiation may kill (shield yourself).

No. This sounds like a solid core nuclear rocket. Like NERVA or Dumbo. It's not that different from a plain old nuclear reactor. There's a core with the uranium rods in the middle inside an enclosed metal shell which heats the liquid hydrogen or liquid ammonia reaction mass outside that then gets ejected outwards. The only way it would leak radiation is if the metal containment failed and even then it would be a much lower level of radiation than a nuclear explosion. It would be more akin to a nuclear power

Exactly.What could go wrong ?Rockets have, at best, 98% reliability (Using old and proven tech, new one is muuch wooorse.).that means that 2% of the time, they explode and get dispersed in the atmosphere, low or high, soon or late.So it's a very very very very very very bad idea to send fissile material to orbit and then to escape velocities.(the small quantities of the mars rovers and similar RTG powered probes are only comparable to a very weak Hiroshima in mass)

What could go wrong ?Rockets have, at best, 98% reliability (Using old and proven tech, new one is muuch wooorse.).that means that 2% of the time, they explode and get dispersed in the atmosphere, low or high, soon or late.So it's a very very very very very very bad idea to send fissile material to orbit and then to escape velocities.

I couldn't find any totals broken down by type of test, and I don't really want to add them all up, but about 20% of US shots were atmospheric, and it looks like most of the multi-megaton bombs were atmospheric. Quite a bit more than your 10%.

"Badly contaminated" seems similarly hyperbolic. The tests were detectable, and you didn't want to be downwind of them for sure, but except in those limited areas they don't seem to have been too catastrophic. I'm not sure why you'd say a rocket disintegrating would

Nothing much. Until reactor is started for the first time, it doesn't contain anything that is not found in nature. It's basically more concentrated uranium, so it can be safely disposed of by letting it crash into the sea. And presumably, the reactor is designed in such a way that it won't become critical after immersion into seawater.

There are interesting developments in this area. For example, Kilopower ( https://en.wikipedia.org/wiki/... [wikipedia.org] ) is aimed to replace RTGs since Pu-238 is becoming too scarce. It will produce about 4kW of thermal energy and will be completely passively regulated by natural thermal expansion of components - no moving parts required whatsoever.

Those political donations from BWX really paid off!Why else is a company that has had nothing to do with rocketry of any kind doing this instead of NASA, the Air Force or a University?It's kind of sad because it would be nice to see an atomic rocket instead of vanishing pork money funding a very expensive undergraduate level literature survey.

More likely it is about producing large amounts of energy is space to use rather than chucking crap out the back to make you go. Chuck stuff out the back and you might as well be using elastic bands with rocks as fuel, you know how old rockets really are and we are still using that technology, really quite embarrassing. Engines to be used in space might well look nothing like what you are expecting, especially if they are designed to project fields outwards, blades, rather than inwards, cones. Energy is key

That would be nicer but you'd pick someone with a track record if that was the actual goal, and if there's nowhere with a track record private industry is not where you go since that's the expensive way to do it.

FINALLY !It's been about 50 years that the NERVA program has been on hold - mostly because of the atmospheric nuclear test ban treaties of the time, and also the space nuclear bans related to those test bans.

Nuclear thermal is a nice technology for some missions (but probably not Mars where the delta-V isn't all that high). The problem is that I don't see it as political realistic. There are political issues with radioisotope generators on deep space probes - for example the proposed Europa lander will have a very limited lifetime because it will only have chemical batteries.

I think a NTR could be launched safely if it hasn't been turned on yet, but I also think that there is not a snowballs chance in hell o

If only people would stop giving money to scientifically ignorant, no that's not fair... scientifically combative organizations like Green Peace, we could move forward. Green Peace and Sierra Club combat things like this because they want more money and they keep frightening people into thinking they're bad. Anything is bad if it's not used right. Just like the Japs with their power plants. Not just one, Three nuke plants in an area known for being flooded and the dimwits put the generators in the basement

When I took Intro Chemistry at San Jose State University (before they kicked me out for playing too much Magic: The Gathering [amzn.to] into the wee hours), we had a tour of the research reactor in the basement of the science building. We were reassured that the reactor was completely safe. If it ever did go kablooey (extremely unlikely), it would only blow up the building. Rest assured that I went into computers instead of nuclear science.

Why is thorium never consider. It is a safer fuel, liquid in reactor use, easy to contain when things go bad, being a liquid you can drain it off into several containment vessels and the waste product much easier to contain as most of it is lead.

Why? Same reason we use uranium; can't make a bomb. Almost all thorium byproducts are at the end of the fission scale, but Thorium is fairly easy to find in nature; easier than uranium.

Hell the lead might make good ejection mass for a ship in flight. Solar wind woul

It seems that less enriched fuel would require a larger, heavier engine. They may actually build one, but up front after thinking it out, or eventually after seeing the practical problems, they will discard the LEU engine concept.

as in, how many million tons of chemical fuel to boost the reaction mass (water) into low orbit?Nuclear engines do not have higher specific impulse than LH2-LOx and thus, the reaction mass will be GREATER and require a larger chemical rocket to hit LEO.Thus a nuclear engine will have to be a low delta-v ion/magnetic drive.So, reaction mass will go up separately, on Chemical rockets and will be even MORE expensive.

There are existing reactors in the hundred-kilowatt range and potential for development of megawatt range reactors, which are feasible for space - spent about 3 hours today just reading up on VASIMR [wikipedia.org] and MPD [wikipedia.org] engines, which - when combined with modern designs for nuclear reactors - will open up speedy access to the entire solar system, and far beyond.
Check this list of reactors - old, new and potential - and the energy outputs we've already achieved:
http://www.world-nuclear.org/i... [world-nuclear.org]
The future of space ex

Go watch the Boondocks, most black people know all about the lunacy of the left and the contradiction between modern money-making black "pop culture", and Martin Luther King's noble and righteous motives and goals.

MLK envisioned a future where people would be judged by the quality of their character, rather than the colour of the skin. A "colour-blind society" where people would succeed based on hard work, honesty and justice for all. He never said anything about silencing people who were white from speakin

I'm replying as AC because I modded-up this and I think questions like this should be answered from time to time, even though I disagree with the apparent sentiments.

Firstly, "paying down the national debt" isn't necessarily as useful as one might think. Certainly, avoiding indebtedness to foreign powers may be of strategic importance, and rapid expansion of national debt for big spending programs might stoke high inflation that drives economic instability. However, most of the national debt (along with most money in the economy) is funded with money that has been created from thin-air by private-sector banks, and perhaps laundered through the economy to look more real than it is. Paying-off the original debts that created the money causes it to disappear with the debt but it provides profit in the form of interest for the banks that created the money in the first place. Very little actually goes to cover capital and interest for the deposits of any real investors, and even those originated mostly in debt to generate new assets that have been laundered and liquidated into cash for deposit. This is the world of fractional reserve banking, where almost all money in the system is born out of debt and inflation.

Now to the main point about why do this instead of "more worthwhile things we could be doing, such as curing cancer, solving world hunger, or reducing our impacts on climate change". Of course those are important and, quite rightly a good deal more money –many billions of dollars– already goes into those things than the 19 million dollars going into this project.

But blue-sky technology and pure science reap huge benefits in the long term and that simply can't be foreseen. Copernicus, Galileo, Tycho Brahe, Kepler and Newton were concerned with the motions of planetary bodies and the moon. They paved the way for the foundations of the science of mechanics which is one of the pillars of all of modern engineering and science. Franklin, Faraday and many others tinkered with electricity and magnetism, and Maxwell synthesised a theory from their experiments which gave another of pillar foundations of everything we have now. Even the highly abstract theories of Quantum Mechanics and General Relativity, formulated a century ago, now have a big impact on our everyday lives.

Everything I've described (albeit in a very brief and shallow manner) is the basis for things like MRI, CT and PET scanners, computational drug discovery, understanding climate change, GNSS/GPS and countless other technologies that have the power to benefit everyone. There are bigger political decisions to be made that will have more impact than anything gained by switching funding from atomic rockets to feeding the starving. Consider the cost of building a 2000-mile wall. And if you want another perspective, consider that, in the US alone, about $200 billion is spent each year on advertising.

Personally I have no desire to move to Mars; it's way more hostile than America would have been for early settlers, but that doesn't mean we shouldn't invest a relatively small amount. One can't imagine the long-term benefits that humanity might eventually reap from the effort.

I haven't bothered with references but if you're curious and if you really care you can easily find plenty to read about any of this.

It's a study into feasibility, not a launch program. Presumably, given Musk's talk of Mars, SpaceX is also doing a study and the can be compared. It's pretty normal to look at multiple options for something so bold, before committing, or taking on faith the first organisation to say they can do it. SpaceX has no track record in deep space (NASA does), so I'd want to see a detailed work up from SpaceX too before signing a contract.

For high-mass, Hohmann-transfer spacecrafts bound to Mars, nuclear really isn't the best propulsion option even in the long run. It's basic physics. At the low delta-Vs required for the flight, the mass ratios and volumes required are disadvantageous for nuclear, as is mined mass usage from all hydrogen sources with the exception of perhaps mining hydrogen directly from Saturn or one of the other smaller gas giants.

True, but even slight increases (1-2 km/s in case of Mars) cut off most of the time; afterwards, there's only diminishing returns. And we can do extra 1-2 km/s chemically just fine. Not to mention that arrival speed increases much more sharply than departure speed (and you don't want to crash into Mars at 20 km/s). However, in case of nuclear thermal propulsion, the use of asteroid-mined propellant only breaks against chemical propulsion after reaching like 10-12 km/s (that's from LEO, so about 18-20 km/s o

It's true, but the benefits are questionable then. Hell, they're somewhat questionable even with hydrogen, since solar thermal propulsion has slightly higher Isp because of the heat exchanger being inert. But maybe a nuclear rocket would be good for jumping around Mars, using CO2 as a working fluid.

However, they work much better for non-Hohmann transfer orbits. Or non-lowest dV Hohmann transfer orbits. There are advantages to getting to Mars more quickly. Keeping the crew alive being one of them.

Even SpaceX admits that for more distant missions (far outer planet destinations, oort cloud, etc), scaling chemical rockets is not sufficient. Nuclear rockets are also interesting for Venus, delivering crew and payload between the habitable layer (~54km) where breathable air is a lifting gas that can loft a colony, and orbit. Some of Venus's great advantages, like having nearly Earthlike gravity and thus no concerns about wasting like exist for the moon and (to a lesser extent) Mars, are also disadvantages, in that it's also nearly Earthlike difficulty to get to orbit. Furthermore, unlike Mars where your rocket rests on the ground, with Venus you have to support its fully fueled mass. While it's possible to get out with two-stage chemical rockets and re-dock the returning stages, you get much better mass fractions with nuclear. Even though nuclear pretty much only works with hydrogen propellant (the ISP drops in linear proportion to the atomic mass of the propellant), and hydrogen is not particularly common on Venus, the low propellant requirements mean that a nuclear rocket can use less hydrogen than most low-hydrogen rocket propellants that could be used were the ascent vehicle a two-stage chemical rocket.

I'm sure lots of people are going to be discussing NERVA in this comments section. It's important to realize that NERVA is obsolete technology, and there are much better designs available at present. NERVA's biggest problem was its awful thrust to weight ratio. One of the first realizations since then was that you can make a nuclear rocket with a LOX "afterburner"; at liftoff, you use LOX to vastly augment the thrust (the resulting ISP, while nothing like pure hydrogen nuclear-thermal, is still well above that of normal hydrolox). Once the high liftoff thrust requirements are no longer needed, the rocket transitions to pure hydrogen thrust for much higher specific impulse.

A variety of airbreathing modes have also been investigated which can strongly increase thrust and/or specific impulse further - thrust augmentation, nuclear scramjets, nuclear-driven turbojets, etc. Also, there have been general improvements in nuclear technology to allow for transferring higher energies to the hydrogen steam since then, as well as a number of yet-to-be-proven concepts. For example a fission fragment reactor can theoretically get the hydrogen much hotter than the reactor itself; in such a system, the goal is to (as much as possible) capture only neutrons in the fuel and only thermalize fission fragments (which carry most of the energy) in the hydrogen. But you definitely wouldn't pursue a fission fragment reactor with LEU....

Well, on the Falcon Heavy page they list payload to Pluto and escape velocity is only 0.39 km/s [imgur.com] (0.03+0.02+0.11+0.20+0.03) more delta-v than that so anything inside the Sun's gravity well like the far outer planets is quite reachable by chemical. If you do ITS-style fueling in orbit or slingshot around Jupiter probably with a decent size payload too. The Oort cloud is a lot further out though, Voyager is at 139 AU and the lowest estimate for where it might begin is 2000 AU so like 500+ years even with all t

If Humans were logical creatures we'd stop funding all military, form a planetary government, and stop all talk of Martian colonization since that's not required and diverts resources from social programs and science.

If Humans were logical creatures we'd stop funding all military, form a planetary government, and stop all talk of Martian colonization since that's not required and diverts resources from social programs and science.

That makes sense if you look no farther than your navel, and plan for no later than next week. But on a long enough time scale, a rock is going to come along and wipe out our species, and we also develop ancillary technologies while figuring out how to explore space which pay dividends right here on Earth. Unfortunately, much of our leadership is just as short-sighted as you are.